For example, the NFS (Network File System) of Sun Microsystems Inc. provides such a system for plural computers interconnected over a network, in which, in a well-known manner, a file system of a remote computer is caused to appear as if it is a local computer file system for a directory supervision so that the computer can access a file of the remote computer in the same way as the local file system. However, the file is processed by a local computer, such that file processing cannot be carried out on the remote computer.
Moreover, a remote shell mounted on a UNIX system is a script language configured for executing commands on a remote computer, as described in Document 1 (Unix Network Programming, W. Richard Stevens, Prentice-Hall, 1990). In this script language, the executing computer is specified and the command specified by the script is executed on the specified computer, providing, however, that one script is interpreted on only one computer.
For executing the command on plural computers, there is no alternative but to provide plural scripts each designating a computer for execution, and to invoke the plural scripts sequentially as remote shells in association with each of the plural computers.
As a technique for continuing execution across or over plural computers, there is known a movable agent system.
For example, in a telescript technology of General Magic Inc., USA, an agent moves among different computers under a “go” command, as described in Document 2 (Publication of JP Patent Kokai JP-A-7-182174. In order for an agent to have communication with another agent, the agent needs to be moved at the outset to a special site called a “place” where a counterpart agent exists. In other words, communication is possible only between agents existing in the same place. Although the telescript technique features the itineration across plural computers to receive services, it suffers a drawback that place management needs to be performed separately from service management and that one agent cannot access plural computers in parallel.
The “Agent Tcl”, also called “D'Agent”, disclosed in Document 3 (“William Cockayne and Michael Zyda, Mobile Agent, Manning Publications Co., 1997”), is a mobile agent developed by Dartmouth University, USA. This mobile agent is based on a shell script language, called “Tcl” (Tool Command Language), to which is added a movement function by an “agent_jump” command. This “Tcl” can be utilized as a simple shell and represents a shell script language that can be used more readily by a user than the program language exemplified by telescript.
However, even in the “Agent Tcl”, agent movement across the computers is performed by a movement command and supervised by a directory separate from the directory for the resources in the computer. The computer and the resources in the computer are supervised by separate directories, such that a management of the movement command is independent of a management of the computer resources.
On the other hand, since an agent can exist only in one computer, the resources of plural computers cannot be handled in parallel.
In, e.g., Document 4 (JP Patent Kokai JP-A-10-149287), there is disclosed a mobile agent system of the predicate logic type in which an action of the script language for causing the agent movement by a [go to] command can be stated as a predicate.
In the system described in Document 4, the script language can describe the agent movement, however, it cannot supervise the directory together with the resources furnished by the computer. Moreover, similarly to other mobile agent languages, the script language can not access the resources of plural computers in parallel.
In, e.g., unpublished Document 5 (JP Patent Application No. 11-047015, not published as of the filing date of the present Japanese application, now Kokai Publication JP-P2000-244426A published Sep. 8, 2000), there is described a system which not only has an agent movement command and is able to move a program being executed to different computers but also has a function of permitting an agent to perform execution in parallel across plural computers such that a program unifies services present in distribution across plural computers to supervise the services in a distributed and synchronous fashion to provide a service over a network. However, commands for movement and management of the computer resources are performed independently of each other, such that a user cannot easily access computer resources distributed over the network. However, there is much to be desired in this system, likewise other techniques disclosed by the published documents.